There are generally four types of automotive driveline systems. More specifically, there exists a full-time front wheel drive system, a full-time rear wheel drive system, a part-time four-wheel drive system and an all-wheel drive system. Most commonly, the systems are distinguished by the delivery of power to different combinations of drive wheels, i.e., front drive wheels, rear drive wheels or some combination thereof. In addition to delivering power to a particular combination of drive wheels, most drive systems permit the respective driven wheels to rotate at different speeds. For example, when turning, the outside wheels generally rotate faster than the inside wheels and the front wheels generally rotate faster than the rear wheels.
Driveline systems also include one or more constant velocity joints (CVJ). Such joints, which include by way of example and not limitation, the plunging tripod type, a high speed fixed type, along with any other known types are well known to those skilled in the art and are employed where transmission of a constant velocity rotary motion is desired. A typical driveline system for a rear wheel or all-wheel drive vehicle, for example, incorporates one or more constant velocity joints to connect a pair of front and rear propeller shafts (propshafts). The propshafts transfer torque from a power take-off unit generally located about a front axle of the vehicle to a rear driveline module generally located about a rear axle of the vehicle. Similarly, a driveline system for a front wheel drive vehicle incorporates one or more constant velocity joints to transfer torque from the power take-off unit to the propshaft(s).
At certain rotational speeds and resonant frequencies the above referenced propshafts typically exhibit unbalanced rotation and thus undesirable vibrations. These vibrations traditionally result in bending or torsional forces within and along the length of the respective propshaft. Such bending or torsional forces as a result of the unbalanced rotation are neither desirable nor suitable in the operation of the driveline systems of most vehicles.
Accordingly, various dynamic dampers or mass dampers are utilized to suppress the undesirable vibrations that are induced in the rotary propshaft as a result of the natural frequencies of the propshaft amplifying input vibrations from the engine or other driveline components, such as gears, bearings, etc. These dampers are often installed or inserted directly onto or into the propshaft. The dampers are designed to generate a prescribed vibrational frequency and damping adjusted to the dominant frequency of the undesired vibrations. The damper converts or transfers the vibrational energy of the propshaft to the damper by resonance with the addition of an additional degree of freedom, and eventually absorbs the vibrational energy of the propshaft. Therefore, the damper attempts to cancel or negate (by splitting the resonance into two smaller resonances) the vibrations that are induced onto or caused by the rotary propshaft in normal operation of the driveline system of the vehicle.
Many dampers generally include a mass member disposed between a pair of ring-shaped fixing members and a pair of connecting members. The connecting members connect the ends of the fixing members to the mass members. However, many of these traditional dampers are not easily tunable to specific frequencies and have difficulty controlling the frequency for which the tuned absorber has been specifically designed to resonate without extensive redesign of the damper and the propshaft for each automotive vehicle driveline system. Further, many traditional dampers are developed for installation directly into the rotary propshaft. However, some these dampers are not capable of maintaining their alignment and become eccentric producing an undesirable vibration due to imbalance.
A typical energy absorber for insertion within a propshaft may include materials with temperature dependent properties. These materials include rubber, where the frequency and damping rate of the rubber changes with temperature changes. An example of such a prior art absorber is shown in FIG. 1. FIG. 1 illustrates a rear propshaft 54 with a prior art absorber 270. The absorber 270 includes a rubber portion 272 coupled to an inner propshaft surface 64, and an absorber mass 274. The rubber portion 272 is generally annular in shape while the absorber mass 274 is generally cylindrical. During rotation of the propshaft the rubber portion 272 operates to dampen vibrations. However, as stated above, the frequency and damping rate of the rubber changes with temperature changes. And a change in these properties will change the tuning of the absorber, which will, in turn, potentially deteriorate the effectiveness of its bases.
Therefore, there is a need in the art for an improved internal absorber. There also is a need in the art for an internal absorber that is simple to install and modify to match specific frequencies and dampening levels of various vehicle driveline systems, as well as an absorber that is temperature independent.